Development of Thyroidal Responsiveness to Estrogen in the Maturing Rat

Abstract

Summary

The incidence of thyroid disorders around the time of puberty is frequent in human females. The influence of estrogen on thyroid function during this period has been controversial. Female rats hypophy-sectomized at 21, 30 or 50 days of age were treated with either 17β-estradiol (E₂) or TSH or a mixture of E₂ and TSH. Determinations were then made of thyroidal ¹³¹I-uptake, organic ¹³¹I, and ¹³¹I excretory patterns. In 21-day old animals, E₂ alone had no effect on thyroidal ¹³¹I uptake, whereas in 30-day or older animals E₂ significantly increased ¹³¹I uptake. TSH or TSH-E₂ combinations markedly increased ¹³¹I uptake in both groups. Thyroidal ¹³¹I was shown to be almost exclusively protein-bound in each instance. No difference was observed between 21 and 30-day old rats with respect to ¹³¹I excretory patterns, except for decreased urinary output in the TSH-E₂ groups; this decrease, however, appeared to be partially attributable to an increased thyroidal uptake of iodine in these animals. The results suggest that the thyroid gland becomes responsive to estrogen only at or around the time of puberty.

This investigation was supported in part by USPHS Training Grant No. HD00112-06 from the National Institute of Child Health and Human Development, NIH.